Anti-vibrational holding device for an electric motor

ABSTRACT

The invention relates to an apparatus for vibration-insulated mounting of an electric motor ( 20 ), in particular a blower motor, having a first housing part ( 10 ), which encloses at least one pole ring ( 22 ) and magnets ( 24 ) of the electric motor ( 20 ) and has at least one opening ( 14, 16 ), through which the shaft ( 18 ) of the motor ( 20 ) reaches, and having a second housing part ( 54 ), which is embodied as a motor flange for securing the electric motor ( 20 ) to a carrier element, for instance a motor vehicle heating and/or air conditioning system, and at least partly embraces the first housing part ( 10 ) in the axial direction of the motor shaft ( 18 ).  
     It is proposed that on the outer circumference ( 26 ) of the first housing part ( 10 ), a plurality of radially extending, relatively flat plastic spokes ( 28 ) are provided, which engage associated, radially and axially extending recesses ( 57 ) of the second housing part ( 54 ), and which in the region of their radially outer end ( 32 ) have connecting means ( 36 ) for securing them to the second housing part ( 54 ).

[0001] The invention is based on an apparatus for vibration-insulatedmounting of an electric motor, in particular a blower motor, asgenerically defined by the preamble to the independent claim.

[0002] Blower motors for heating and air conditioning blower systemsthat are used in vehicles, for instance, are as a rule decoupled interms of vibration from the vehicle, in order to reduce the transmissionof structure-borne sound from the motor or blower unit to the vehiclebody and hence the passenger compartment of the vehicle.

[0003] Current methods of securing such motors comprise inserting thecomplete motor into a plastic housing or metal housing, on which aflange is provided for connection to the air conditioning system.Normally, rubber in the form of suitably shaped rubber elements isplaced between the motor and the motor housing or into the flange, inorder to damp sources of vibration of the air conditioning system or thevehicle body and to suppress noise that would be irritating to thedriver or his passengers in the passenger compartment of the vehicle.

[0004] A primary source of vibration in d.c. motors is the commutation.The commutation occurs when the copper windings of the armature carrycurrent during the operation of the motor. During each revolution of thearmature shaft, current is carried in each direction through theexisting windings of the motor. Under the influence of a permanentmagnet field, the conduction of current in the windings causes areaction that is transmitted onward in the form of a torque pulse. Thenumber of windings, multiplied by two and taking the rpm rate intoaccount, is the frequency of the commutation and thus the number oftorque pulses transmitted by the motor per unit of time.

[0005] Accordingly, the commutation transmits torsional vibration intothe heating or air conditioning blower system in accordance with thefluctuation or variations in the torque pulses. If rubber or suitabledecoupling elements of rubber are placed between the flange and themotor housing, it is assured that reduced torsional vibration pulseswill be transmitted into the heating and air conditioning blower system.The rubber is a mechanical filter, which prevents excessive vibration orthe penetration of elevated vibration into the heating and airconditioning system and thus brings about a partial mechanicaldecoupling of the components.

[0006] In actual use, various possibilities exist of using rubberelements or decoupling elements of rubber between the housing flange orbetween the motor and the motor housing in order to damp precisely thesevibration pulses.

[0007] German Patent Disclosure DE 43 34 124 A1, for instance, disclosesan apparatus for receiving an electric motor that achieves an especiallylow-vibration and hence noise-damping effect by providing that betweenthe inner walls of this receiving apparatus and the outer walls, facingthem, of the motor housing, at least one elastic damping element isdisposed, which is braced on the walls facing one another of thereceiving apparatus and the motor housing.

[0008] These elastic damping elements, which in a preferred embodimentof the apparatus of DE 43 34 124 A1 are suitably shaped rubber elements,represent increased expense for assembly and material, whichunnecessarily increases the costs for such an apparatus. In particular,rubber elements and rubber damping elements represent a problem for theassembly lines in industrial production, since they can be integratedinto the corresponding apparatuses only by means of time-consumingmanipulating processes.

[0009] From U.S. Pat. No. 4,063,060, a retaining device for an electricmotor is known in which three rotationally flexible leaf-spring-likesteel retaining arms are provided, which are offset from one another bythe same circumferential angle, are fastened in the manner of raysbetween the electric motor and the receiving housing, and are each boundby one end, with the interposition of elastic buffers, to an inletcollar that is solidly connected to the receiving housing.

[0010] Because of the three-point suspension in a single plane of theelectric motor in U.S. Pat. No. 4,063,060 and the low spring constant ofthe retaining arms in the direction of torsion, this motor executesrelatively major oscillating and tilting motions, which in the elasticelements, especially the buffers, engender shear forces that rapidlycause material fatigue and damage. The service life of this knownretaining device is therefore severely limited and is inadequate for usein motor vehicles, in which the elastic elements must also absorbvibration that is caused by external impacts from the roadway on theelectric motor.

ADVANTAGES OF THE INVENTION

[0011] The apparatus for vibration-insulated mounting of an electricmotor according to the invention, as defined by the characteristics ofth independent claim, has the advantage over the prior art that thevibration-insulating elements are plastic spokes, which on the one handassure that the electric motor is decoupled in terms of vibration from asecond housing part that at the same time serves as a motor flange forsecuring the electric motor in the vehicle. Secondly, thevibration-insulating plastic spokes of the invention take on theadditional task of connecting the two housing parts—that is, the motormount and the motor flange—to one another.

[0012] In their function, the plastic spokes of the invention representa mechanical filter, which decouples the irritating torque pulses of themotor from the heating and air conditioning blower system, so that lessvibration is transmitted to the system, and the noise level is reduced.This design has the advantage that the plastic spokes act as springelements, without having to use rubber or rubber elements to damp theincident vibration.

[0013] Advantageous embodiments of the apparatus of the invention willbecome apparent from the characteristics recited in the dependentclaims.

[0014] In an advantageous embodiment of the apparatus of the invention,the housing parts are of plastic. This embodiment makes a markedreduction in weight possible for the apparatus for mounting the electricmotor. In particular, the housing parts can be made by injectionmolding, making it easy to embody additional components and carrierelements on the housing. In this way, a shaft bearing can for instancebe sprayed on directly, or a mount for the brushes or correspondingchoke coils can be shaped directly on the motor mount. The motor housingcan also be embodied directly of plastic.

[0015] The entire apparatus of the invention can thus be manufactured,including the decoupling elements, of virtually the same material, whichmarkedly simplifies the process of producing such motor mountapparatuses.

[0016] One embodiment that is simple to achieve and is especiallyadvantageous is obtained if the vibration-insulating plastic spokes aresprayed directly onto the corresponding first housing part of theapparatus and thus embodied integrally with it. Then additionalconnecting means and the problematic transition to different materialsare unnecessary.

[0017] A good vibration-insulating effect of the plastic spokes isobtained if the plastic spokes are embodied as relatively flat. Forinstance, trapezoidal plastic spokes, in which with increasing radialdistance from the motor the axial length of the spoke surface decreases,demonstrate very good damping properties.

[0018] The damping characteristics of the vibration-insulating motormounting according to the invention can be varied individually, forinstance by way of the number and precise shaping as well as thethickness, height, radial length and conicity of the plastic spokes andadapted to the various requirements of different types of motor andvarious intended uses. An optimal number of plastic spokes proves forinstance to be in the range from three to six, which are distributedover the circumference of a first housing part, in which the pole ringand magnets of the electric motor are for instance secured.

[0019] Plastic spokes that are designed to be soft in their transversedirection, that is, in the axial direction to the motor, enable markedlyimproved decoupling of the torsional torque-vibration pulses and thusprevent them from being imported into the heating and air conditioningblower system or into the vehicle body. The rigidity of the plasticspokes in the transverse direction is selected such that when the motoris running at low-frequency rpm, the torsional torque pulses aredecoupled by the plastic spokes from the motor flange and the otherappended parts.

[0020] A further advantageous design is given the apparatus of theinvention if the plastic spokes, on each of their radial ends remotefrom the motor, have additional damping elements, which are essentiallyperpendicular to the radial direction of the plastic spokes.

[0021] By suitable configuration of these second damping elements on theends of the plastic spokes, it is possible to favorably affect theentire damping characteristic of the spoke elements.

[0022] These smaller damping elements or spring elements, which areperpendicular to the radial primary spoke direction, assure additionaldamping of the sources of vibration at higher frequencies. In this way,the filtering action of the motor housing of the invention can beexpanded over a wider frequency range of unwanted vibration. If thesespring elements are likewise made of plastic, then they can be shapeddirectly, together with the radial spoke elements and the first housingpart, which avoids having to mix materials and thus represents apronounced simplification of the production process.

[0023] By way of their precise size and shape, the dampingcharacteristic of these additional damping elements and thus of theentire apparatus of the invention can be optimized. An advantageousshaping of these second damping elements is obtained if they extend atleast over the entire axial length of the radial end, remote from themotor, of the plastic spokes, so that a uniform transition between thetwo damping elements is obtained.

[0024] In this way it is likewise possible to provide the dampingelements, on each axial end toward the second housing part, with one ormore pegs, which engage suitably shaped indentations in the recess ofthe second housing part. These pegs are secured in the second housingpart and thus assure a stable connection of the two housing parts, whichnevertheless assures the desired decoupling in vibration terms of thetwo components (housing parts). For instance, the pegs can be riveted byultrasound to the damping elements in the second housing part, which isa simple and secure fastening method. It is understood that all otherconnection options familiar to one skilled in the art, such as gluing,friction welding, or fusing are also conceivable.

[0025] To further increase the connection strength, in an advantageousembodiment of the apparatus of the invention the recesses provided inthe second housing part, which receive the plastic spokes of the firsthousing part, can taper conically in the axial direction, that is, inthe direction of the motor shaft, specifically in such a way that thewidth of these recesses decreases in the direction of increasingdistance from the first housing part. In this way it is attained thatthe plastic spokes, on their side toward the second housing part, can beclamped into the recesses of the second housing part. This assures alarger bearing area between the two housing parts and thus increases themechanical stability of the apparatus of the invention.

[0026] Still another improvement in the damping properties for theapparatus of the invention is obtained if the damping elements locatedon the radial ends of the plastic spokes are embraced by rubberelements. Advantageously, these rubber elements come to rest between thedamping elements of the plastic spokes and the walls of the recesses ofthe second housing part.

DRAWING

[0027] Further advantages of the apparatus of the invention can belearned from the description and the drawing.

[0028] In the drawing, exemplary embodiments of the apparatus of theinvention are shown. The description, drawings and claims includenumerous characteristics in combination. One skilled in the art willalso consider these characteristics individually and put them togetherto make useful further combinations.

[0029] Shown are:

[0030]FIG. 1, a schematic plan view on a first housing part of theapparatus of the invention, in a first exemplary embodiment;

[0031]FIG. 2, a section taken along the line AA of FIG. 1;

[0032]FIG. 3, a perspective view of one exemplary embodiment of aplastic spoke;

[0033]FIG. 4, an exemplary embodiment of a plastic spoke with anadditional rubber element mounted on its radial end;

[0034]FIG. 5, a schematic plan view on the first housing part, insertedinto the second housing part, of the apparatus of the invention in thefirst exemplary embodiment;

[0035]FIG. 6, a second, alternative exemplary embodiment of a firsthousing part of the apparatus of the invention;

[0036]FIG. 7, a further elevation view of the second exemplaryembodiment of the first housing part of the apparatus of the inventionof FIG. 6;

[0037]FIG. 8, an exploded view of an exemplary embodiment of theapparatus of the invention; and

[0038]FIG. 9, a perspective view of the first and second housing parts,inserted into one another, of the apparatus of the invention inaccordance with the second exemplary embodiment.

[0039] In FIG. 1, a first housing part 10 of the apparatus 12 of theinvention is shown schematically. The housing part 10 in the exemplaryembodiment of FIG. 1 is approximately cylindrical in shape, and on eachof its axial ends it has a respective opening 14 and 16, through which ashaft 18 of an electric motor 20 can be guided out of the housing of theapparatus. The openings 14 and 16 can be closed by suitable caps, whichcan also comprise a different material from that of the first housingpart 10. For instance, these caps can receive a brush holder part thatbelongs to the motor, or a bearing for the electric motor shaft, orother motor components.

[0040] A pole ring 22 and two segments of a permanent magnet 24 of theelectric motor 20 of the apparatus 12 are inserted into the firsthousing part 10. In addition to the two-segment permanent magnet 24shown here, it is understood that multi-pole magnets can also be used inthe apparatus 12 of the invention.

[0041] On the outer circumference 26 of this housing part 10, spokes28—in this exemplary embodiment, there are four spokes—are mounted,pointing radially away from the housing surface 26. The spokes 28 arerelatively flat in shape; that is, their thickness 30 is markedly lessthan the corresponding radial and axial lengths of the spokes 28. Thisrelatively flat form of the spoke elements 28 advantageously enablestorsional vibration of the first housing part to be decoupled, since acorresponding deformation (torsion) of the spokes 28 is possible.

[0042] A typical size for the thickness 30 of the spokes is on the orderof magnitude of 1 mm, while conversely the radial length of the spokesis higher by one order of magnitude, and typically varies within a rangeof from 1 to 5 cm.

[0043] The spokes 28, which for the sake of better deformability andhence better damping are of plastic, are connected, in this exemplaryembodiment, solidly and integrally to the first housing part 10 and aredesigned as soft in their transverse extent, that is, in the directionof the motor axis. The rigidity of the plastic spokes 28 is selected inaccordance with the model of the motor and the field of use, such thatif the motor 20 is running at its lowest rpm, the torsional torquepulses of the motor are damped and decoupled by the plastic spokes 28.The number of spokes 28 can vary in different exemplary embodiments ofthe apparatus 12 of the invention and is not limited to the numberdisclosed in FIG. 1.

[0044] On their radial ends 32 remote from the housing 10, the spokes 28have additional damping elements 34, which are disposed perpendicular tothe radial direction of the plastic spokes 28. In addition to theplastic spokes 28, these damping elements 34 form a second mechanicalfilter, which decouples the vibration of the electric motor 20 from thebody of a vehicle in which the apparatus of the invention is forinstance accommodated.

[0045] While the plastic spokes are mechanical spring elements whichprimarily assure torsional decoupling, the additional damping elements34 on the radial ends 32 of the plastic spokes 28 also enable a radialdecoupling of incident motor vibration. The damping elements 34 can beembodied integrally with the plastic spokes 28, or they can be connectedto the spokes 28 by other provisions familiar to one skilled in the art.Because of the special connection of the damping elements 34 to theplastic spokes 28 and their connection to the first housing part 10 ofthe apparatus 12 of the invention, the damping properties of themechanical filter, which the apparatus 12 of the invention alsorepresents in its function, among others, can be optimized.

[0046] Located on the underside of the damping elements 34 areconnecting means 36, which are capable of solidly connecting the plasticspokes 28 and thus the first housing part 10 to a second housing part.

[0047]FIG. 2 shows a schematic illustration of the plastic spokes 28,with the damping elements 34 mounted on their radial ends 32, as seenalong a section AA of FIG. 1.

[0048] Also shown in FIG. 2 is a central axis 38, which is equivalent tothe axis of rotation of a motor shaft of the apparatus 12 of theinvention.

[0049] In FIG. 2, reference numeral 24 again designates a magnetdisposed in the first housing part 10, and 22 designates the pole ringof the electric motor 20 of the apparatus 12. The parameters of theplastic spokes 28 that are considered important are their height 40,that is, their length in the direction of the motor axis; their radiallength 42; the thickness 30 of the plastic spokes 28; and theirconicity, or in other words the decrease in the height 40 of the spokes28 with increasing radial distance from the wall 26 of the first housingpart 10.

[0050] By way of these parameters as well as a few others, the dampingproperties of the plastic spokes 28 can be adapted to the particularrequirements of a specialized use.

[0051]FIG. 3 shows an alternative design of the plastic spokes 28 of theinvention in perspective. The plastic spoke 28 shown is shapedintegrally with the first housing part 10 and has a substantiallytrapezoidal shape, with a decreasing height or in other words axiallength with increasing radial distance from the wall 26 of the firsthousing part 10.

[0052] On the radial end 32 of the plastic spoke 28, an additionaldamping element 34 is joined to it, likewise integrally and essentiallyperpendicular to the radial direction of the plastic spoke 28. Thematerial of the damping element 34 can differ from the material of theplastic spokes, in order in this way to achieve an adaptation of thedamping constants to the filter function of the apparatus 12 of theinvention.

[0053] On its end toward a second housing part—in FIG. 3, this is thelower end—this damping element 34 has a peg 44, which serves as aconnecting means 36 for connection to further housing parts.

[0054] The connecting pegs 44 for securing the first housing part 10 toa second housing part of the apparatus 12 of the invention canalternatively be embodied instead directly on the underside 46 of theplastic spokes 28, since the damping elements 34 on the plastic spokes28 are an optional, additional damping component, whose use in otherexemplary embodiments of the invention can also be dispensed with.

[0055]FIG. 4 shows a further exemplary embodiment of the plastic spokes28 of the invention, with additional damping elements 34 on the radialends 32 of the spokes 28. The damping element 34 shown in FIG. 4 isslightly curved outward in the circumferential direction of the housingpart 10 but is disposed essentially perpendicular to the radialdirection of the plastic spokes 28. The spokes 28 in this exemplaryembodiment, or their radial end 32, as well as the adjoining dampingelements 34, are surrounded by a common, additional rubber element 48.On its underside 50, this rubber element 48 has an opening 52, throughwhich the respective connecting peg 44 of the spoke 28 can be passed tofasten it to a second housing part. The additional damping rubberelement 48 comes to rest between the plastic spoke 28 of the firsthousing part 10 and a wall of a recess, receiving this spoke 28, of asecond housing part.

[0056] A rubber element 48 of this kind is equivalent to a third filter,which decouples the vibration of the motor and which is disposed interms of its action parallel to the mechanical vibration filters thatthe plastic spokes 28 with the damping elements 34 on their radial end32 represent.

[0057]FIG. 5 shows a simplified schematic drawing, showing the firsthousing part 10 with the appended plastic spokes 28, with this firsthousing part inserted into a second housing part 54 of the apparatus 12of the invention. This second housing part 54 is embodied in the form ofa motor flange and carries devices 56 with which the motor flange 54 andthus the entire apparatus 12 of the invention can be mounted on acarrier element, for instance of a vehicle heating or air conditioningsystem.

[0058] The plastic spokes 28 of the first housing part 10 come to restin recesses 57 of the second housing part 54 of the apparatus 12 of theinvention. By way of the peglike connecting elements 36 on the undersideof the damping elements 34 of the spokes 28, the first housing part 10is solidly joined to the second housing part 54.

[0059]FIG. 6 is a perspective view of a second exemplary embodiment of afirst housing part 10 of the apparatus 12 according to the invention.The selected viewing direction is from the standpoint of the receivingsecond housing part. In this exemplary embodiment, the first housingpart 10 has three plastic spokes 28, on whose radial ends 32, remotefrom the housing, damping elements 34 are mounted, analogously to thoseshown in FIG. 3. Also visible in FIG. 6 is a connecting peg 44 on thelower end of damping elements 32 of each of the plastic spokes 28.

[0060] In the first housing part 10 of the exemplary embodiment of theapparatus 12 of the invention shown in FIG. 6, the pole ring 22 and twomagnet segments 24 can be seen. From the view through the housing 10, ahousing cap 58 of the housing part 10 is also visible; in this exemplaryembodiment, it is joined integrally to the first housing part. The cap58 has a central opening 60, into which a bearing 62 for a shaft 18 ofan electric motor 20 of the apparatus 12 is inserted. Other visibleopenings 64 in the cap 58 allow motor components to pass through themand provide for cooling of the electric motor 20.

[0061] In FIG. 7, the exemplary embodiment of FIG. 6 is shown again in adifferent but also perspective view, for the sake of clarification. Thethree plastic spokes 28, mounted on the outer circumference 26 of afirst housing part 10 are clearly apparent, with additional dampingelements 34 provided on their radial ends 32 and with the connectingpegs 44 for securing this housing part 10 to a further housing part. Thehousing cap 58, again embodied integrally in this exemplary embodiment,has various fastening elements 66 on its outside for components of theelectric motor 20 of the apparatus 12 of the invention. As examples,only two choke coils 68 for the supply of electricity to the motor 20have been shown in FIG. 7.

[0062] From this view of an exemplary embodiment of the apparatus 12 ofthe invention, the central opening 60, into which a bearing 62 formounting the motor shaft 18 is inserted, can also be seen clearly.

[0063] This first housing part 10, with the electric motor 18 inserted,is thrust axially into a second housing part 54, which also serves as amotor flange, so that the second housing part 54 completely embraces thefirst part 10 radially and partially overlaps it axially.

[0064] The cooperation between the two housing parts of this exemplaryembodiment of the apparatus 12 of the invention is shown as an examplein an exploded view in FIG. 8. FIG. 8 shows the essential components ofan exemplary embodiment of the apparatus 12 of the invention in asimplified view. Between a second housing part 54, acting as a motorflange, and a first housing part 10, embodied as a brush holder andbearing cover unit, the essential components of an electric motor 20 ofthe apparatus 12 are shown. The first housing part 10 carries a polering 22 and two magnet segments 24 of the electric motor 20. Also shownin FIG. 8 is a motor shaft 18, with an armature 70 secured to it andwith a commutator 72. For the sake of simplicity, the necessaryelectrical connections have not been shown but are understood to bepresent. The shaft 18 of the motor 20 is guided via a first bearing 74in the second housing part 54 and via a corresponding bearing 76 in thefirst housing part 10, as is shown for example in FIG. 7 as well.

[0065] The motor shaft 18 protrudes outward past the first housing part10 and is connected to a blower fan 82 via a spring washer 78 and a stopwasher 80.

[0066]FIG. 9 shows the housing parts 10 and 54 put together; in the viewshown, no electric motor is inserted into the housing. The first housingpart 10 engages a central recess 84 in the second housing part 54 and inthe process is partly caught in its axial terminal position by thesecond housing part 54. The diameter of this central recess 84 isselected such that the first housing part 10 of the apparatus 12 isstill movable in this central recess 84. The plastic spokes 28 on thecircumference 26 of the first housing part 10 are aligned withcorresponding recesses 57 in the second housing part 54. These recesses57 in the second housing part 54 taper conically in the axial direction,that is, the direction of the motor shaft, so that once the housing part10 has been inserted, the plastic spokes 28 are clamped in the recesses57 on their lower ends 46, that is, their ends toward the second housingpart 54.

[0067] The second housing part 545 is embodied as a motor flange and canbe connected to a carrier element, such as a vehicle body, via suitablefastening elements that are not visible in FIG. 9. In the second housingpart 54, in the exemplary embodiment shown in FIG. 9, a further recess88 is provided for a control element of the electric motor 20 of theapparatus 12 of the invention.

[0068] The apparatus of the invention is not limited to the exemplaryembodiments presented in this description.

[0069] For instance, the apparatus of the invention is suitable not onlyfor use in blower motors, but can also be used in all kinds of electricmotors and electrical machines.

[0070] It is also understood that other electric motors besides thetwo-segment permanent magnet shown in the exemplary embodiments can beused in the apparatus of the invention.

[0071] The connection of the plastic spokes to the first housing part ofthe apparatus of the invention and the connection of the dampingelements on the radial ends of the spokes to the spokes can also be donein other ways, familiar to one skilled in the art.

[0072] The shape of the plastic spokes according to the invention candeviate from the possibilities shown in the exemplary embodimentswithout departing from the patent scope claimed.

[0073] In particular, plastic spokes that have no further dampingelements on their radial ends are also conceivable for the apparatus ofthe invention.

[0074] The connecting means of the plastic spokes to further housingparts of the apparatus of the invention is not limited to the use of thepegs presented here. It is understood that other connectionpossibilities can be used instead.

1. An apparatus for vibration-insulated mounting of an electric motor(20), in particular a blower motor, having a first housing part (10),which encloses at least one pole ring (22) and magnets (24) of theelectric motor (20) and has at least one opening (14, 16), through whichthe shaft (18) of the motor (20) reaches, and having a second housingpart (54), which is embodied as a motor flange for securing the electricmotor (20) to a carrier element, for instance a motor vehicle heatingand/or air conditioning system, and at least partly embraces the firsthousing part (10) in the axial direction of the motor shaft (18),characterized in that on the outer circumference (26) of the firsthousing part (10), a plurality of radially extending, relatively flatplastic spokes (28) are provided, which engage associated, radially andaxially extending recesses (57) of the second housing part (54), andwhich in the region of their radially outer end (32) have connectingmeans (36) for securing them to the second housing part (54).
 2. Theapparatus of claim 1, characterized in that the first housing part (10)and the second housing part (54) comprise plastic.
 3. The apparatus ofclaim 2, characterized in that the plastic spokes (28) are embodiedintegrally with the first housing part (10).
 4. The apparatus of one ofclaims 1-3, characterized in that the plastic spokes (28) are shapedessentially trapezoidally, preferably in such a way that with increasingradial distance from the motor (20), the axial length of the spokes (28)decreases.
 5. The apparatus of one of the foregoing claims,characterized in that the plastic spokes (28) are soft in theirtransverse direction, that is, the axial direction of the motor shaft(18), so that torsional torque pulses of the motor (20) are damped anddecoupled from the second housing part (54).
 6. The apparatus of one ofthe foregoing claims, characterized in that the number of plastic spokes(28) provided on the first housing part (10) is at least three and ispreferably in the range from three to six.
 7. The apparatus of one ofclaims 1-6, characterized in that the plastic spokes (28), on each oftheir radial ends (32) remote from the motor (20), have additionaldamping elements (34), which are essentially perpendicular to the radialdirection of the plastic spokes (28).
 8. The apparatus of claim 7,characterized in that the additional damping elements (34) on the endsof the plastic spokes (28) likewise comprise plastic and are shapedintegrally with the plastic spokes (28).
 9. The apparatus of claim 8,characterized in that the additional damping elements (34) extend atleast over the entire axial length of the radial end (32), remote fromthe motor, of the plastic spokes (28).
 10. The apparatus of one ofclaims 7-9, characterized in that the additional damping elements (34),on each of their axial ends toward the second housing part (54), have atleast one axially extending connecting means (36), and in particular atleast one peg (44), which engages a correspondingly shaped indentationin the recess (57) of the second housing part (54).
 11. The apparatus ofclaim 10, characterized in that the axial connecting means (36), inparticular the pegs (44) of the additional damping elements (34), aresolidly connected, and in particular riveted, to the second housing part(54).
 12. The apparatus of one of claims 7-11, characterized in that theadditional damping elements (34) are at least partly embraced by rubberelements (48), which come to rest between the damping element (34) ofthe plastic spokes (28) of the first housing part (10) and the wall ofthe associated recess (57) in the second housing part (54).
 13. Theapparatus of one of the foregoing claims, characterized in that therecesses (57) of the second housing part (54), for receiving the plasticspokes (28) of the first housing part (10), taper conically in the axialdirection, so that after the two housing parts (10, 54) have beenaxially joined together, the plastic spokes (28) are partly clamped intothe associated recesses (57).